Protective covers are often used to protect equipment and parts in a wide range of environmental conditions. Corrosion and oxidation are of particular concern, especially in connection with vehicles, airplanes, munitions, weapons and weapons systems and equipment with metal and/or electronic components and the like.
Prior protective covers that address the problem of corrosion are described in U.S. Pat. Nos. 6,833,334, 6,794,317 and 6,444,595. Many of these covers have been found to have fundamental weaknesses that can create a microclimate underneath the cover when in use. The covers have been found to be generally impermeable to or provide good resistance to rain, snow, and offer good water repellency. They generally use a monolithic impermeable coating on one side of the outer fabric layer to provide water resistance.
In recognition of the microclimates formed underneath the cover, as a humid environment cools and condensation forms on the protected equipment, some of the covers utilize a center layer made of super absorbent fibers (typically made from super absorbent polymer—SAP). When the SAP absorbs the condensation it can make the cover extremely heavy when wet and then can freeze in place in a cold environment. The technology also sometimes uses vapor corrosion inhibitors (VCI's that leach out of the cover as moisture passes through the cover and can deposit itself on the equipment leaving a moist residue on the equipment it is trying to protect.
Additionally, current technologies use UV stabilizers in the dyes used to color the cover fabrics and although this offers some level of durability, the cover life is still generally in the range of 9-18 months of effective working life.
There remains a need, however, for more effective covers that provide protection and resistance to penetration of water, wind and sand and that are especially effective with respect to the prevention or at least minimization of oxidation and/or corrosion due to humidity build-up around the covered objects. Additionally, prior art protective covers have been found to be damaged by abrasion and other environmental factors caused by windblown sand, other wind borne particles and UV solar light and therefore, the ideal protective cover should be durable and able to resist abrasion and damage caused by wind, sand and other substances, as well as resist degradation caused by UV energy from the sun.
It is desirable that covers perform in use without degradation or fall-off in performance for an extended period of time, preferably greater than 4+ years. The primary mode of failure of most covers found in use today is a loss in mechanical strength that can be observed in the formation of holes and tearing of the fabric. This loss in strength and durability is the result of molecular weight loss of the base polymer from which the fabric is made via continued exposure to ultra-violet light.
Protective covers of the type described above are designed and engineered to protect key assets both military and industrial that are subject to corrosion and or degradation from exposure to environmental conditions such as rain, fog, snow, wind, relative humidity, ultraviolet light and general pollution such as air borne dust, sand, acid rain etc. Such assets could be military hardware, such as helicopters and armored vehicles, or electronic components such as generators or general ordnance (small to large scale guns). Overall, cover technology by means of air permeable fabrics are proven to offer suitable protection to the assets described.
In addition, occasionally applications occur where a cover is needed to protect and cover explosive materials and or sensitive electronic equipment. Usually materials used to manufacture covers use insulative, synthetic materials, such as polyester or nylon or similar textile woven or knitted fabrics. The risk of a static electrical charge build up occurring via the on-off motion from the described material cover or a charge build up from in-use dynamic movement and flexing of the cover could cause catastrophic failure of the cover and the asset being protected.
Previously some concepts used to impart electrical conductivity or static dissipation properties to cover materials have been tried and evaluated. Most include the use of yarns or threads containing a percentage component of either a metallic (stainless steel or copper sulphate) or carbon to render the yarn and thus the woven or knitted fabric made from the yarn, electrically conductive. Fabrics have been made where the conductive fabric uses 100% electrically conductive yarns or the electrically conductive yarns can be strategically woven or knitted in to the fabric by use of a grid/square pattern or uni-directional design. In each case the conductive yarns which are always present on either outer surface of the cover can be exposed to the environments described herein which in turn leads to the risk of long term durability failure based upon UV exposure and abrasion damage. Further, the cost of imparting such yarns in the finished fabric can be expensive and cost prohibitive.
In many such cover applications described above it is also necessary to provide fire resistance characteristics to the protective covers due to the explosive materials that require protection. This Fire Resistance feature must be provided without impacting the covers air permeability and Moisture Vapor Transmission Rating (MVTR) characteristics, adding weight or impacting Electro-static discharge.
Therefore, what is needed is a fabric cover with a multi-layer construction that uses an outer fabric that is designed to be durable, water-repellant, conforming, and flexible to be shaped and formed to protect the equipment against corrosion and/or oxidation degradation and potential catastrophic failure caused by its exposure to a wide range of environmental conditions. The cover should provide greater than 2 times the current life of a cover and meet the industry requirements of greater than 4+ years of life. Additionally, the cover should address the problem of corrosion by providing a level of relative humidity (RH) management and control while also providing an effective and durable electrical conductive or electro-static dissipative (ESD) performance characteristics to the cover material. A preferred fabric cover should also include Fire Resistance characteristics.
It is important to note that the present invention is not intended to be limited to a system or method which must satisfy one or more of any stated objects or features of the invention. It is also important to note that the present invention is not limited to the preferred, exemplary, or primary embodiment(s) described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention.